Textile apparatus

ABSTRACT

The specification discloses methods and apparatus for twisting, and specifically false twisting, yarns wherein a travelling yarn is constrained to take up a curved path in contact with a rotating curved tube. This causes the yarn to be twisted by engagement with the interior surface of the tube. All parts of the yarn in contact with the tube are twisted at substantially the same speed since the contact path is substantially parallel to the rotary axis of the tube.

United States Patent 91 Gilchrist March 6, 1973 [54] TEXTILE APPARATUS Reginald Selby Gilchrist, 131 Hand- [76] Inventor:

' side Lane, Welwyn Garden City, I England [22] Filed: May 5, 1971 [21] App1.No.: 140,372

52 U.S. c1 ..57/77.3,57/34 ns,57/51, 57/157 rs 51 Int. Cl. ..D02g1/04,D01h 13/28 [58] Field of Search ..57/34 R, 34 HS, 77.3, 77.4, 57/77.45, 156,157 R, 157 TS, 157 MS [5 6] References Cited UNITED STATES PATENTS 3,537,250 11/1970 MacKintosh ..57/77.4

l-luntor ..s7/34 ns Russell et a1. ..57/77.4

Primary Examiner-Donald E. Watkins Att0rneyWatson, Cole, Grindle & Watson [5 7 ABSTRACT The specification discloses methods and apparatus for twisting, and specifically false twisting, yarns wherein a travelling yarn is constrained to take up a curved path in contact with a rotating curvedtube. This causes the yarn to be twisted by engagement with the interior surface of the tube. All parts of the yarn in contact with the tube are twisted at substantially the same speed since the contact path is substantially parallel to the rotary axis of the tube.

13 Claims, 3 Drawing Figures PATENTEU 51975 3,719,035

INVENTOR, (Ea/mm 551m 6/1 (HF/57' ATTORNEYS TEXTILE APPARATUS This invention relates to methods and apparatus for twisting yarns and particularly to false twisting yarn for example in order to crimp or bulk yarns of synthetic thermoplastic material. The term yam as used herein includes monofilament yarns as well as multifilament yarns and tows, split film or fibrous material.

According to one aspect of the present invention yarn twisting apparatus incorporates at least one twisting element which constrains a travelling yarn to take up a curved path in contact therewith and having a rotary yarn engagement surface or surfaces all parts of which are arranged to rotate at substantially identical speeds over the length of the curved contact path.

According to another aspect of the present invention apparatus for twisting yarn comprises a flexible tube constrained to have a curved longitudinal axis and mounted for rotation about its longitudinal axis.

The flexible material of the tube may be a flexible thermoplastic material for example polyethylene or polyvinyl chloride or a suitable grade of polyurethane or rubbers of various types, such as polychloroprene or styrene butadiene.

The tube may be sufficiently self-supporting to retain an open bore, or it may include means for supporting it so as to maintain the bore of the tube open.

The supporting means may be in the form of a helix of spring material such as spring steel with the flexible material forming at least a lining on the inwardly facing surfaces of the turns of the helix.

The lining may be in the form of a helix of which the I adjacent turns are in contact on that side of the tube which has the smaller radius of curvature while on the opposite side, the turns may be spaced apart.

In one embodiment of the invention, the tube comprises a helical spring having a continuous tube of the flexible material secured or supported by the inwardly facing surface of the spring, for example by bonding, or compression.

In another form of the invention, the tube is in fact a helix and comprises a helix of spring material having a' coating of the flexible material on at least the inwardly facing surface of the helix.

The pitch of the turns of the helix in this form of the invention may be such that the successive turns of the helix abut against each other along the portion of the tube which has the smallest radius of curvature along its length, and the successive turns on the diametrically opposite side of the tube which has a greater radius of curvature along its length may be spaced apart.

The radius of longitudinal curvature of the tube may vary along the length of the tube. The tube may be longitudinally curved in the form of part of a parabola so as to have part of its length curved about a smaller radius than another part. However, the tube may be longitudinally curved through an arc of a circle.

The tube may include one or more annular guides of, for example, polished ceramic material, spaced along its length. There may be one such guide at one or each end of the tube.

The tube may be mounted for rotation in one or more bearings. The bearings may be arranged to constrain the tube to maintain its longitudinally curved form while it is rotating about its longitudinal axis.

According to another aspect of the invention-there is provided apparatus for false twisting yarn comprises means for heating a travelling yarn, a flexible tube constrained to have a curved longitudinal axis, means for rotating the tube about its longitudinal axis, and means for linearly advancing a yarn in heat exchange relationship with the heater and through the tube so as to contact the internal wall thereof.

The invention also relates to methods of twisting yarn utilizing apparatus of the above type.

The invention may be carried into practice in various ways but certain specific embodiments will now be described, by way of example, with reference to the ac companying drawings, in which:

FIG. 1 is a schematic elevation of false twist crimping apparatus embodying the invention;

FIG. 2 is a sectional elevation through one form of false twisting apparatus according to the invention, referred to as the head, and also showing, in chaindotted lines an alternative construction;

FIG. 3 is a sectional elevation through an alternate construction of part of the apparatus of FIG. 1.

Referring to FIG. 1, a yarn Y is advanced from a package 1, past a twist stopping and tensioning device 2 to a yarn heater 3 where it is heated.

The heated yarn leaves the heater and passes to a friction twisting head 5 which rotates the advancing yarn by frictional contact and as a result of this rotation, a-twist is inserted into the yarn between the tension device 2 and the friction twisting head 5 and the twist is removed as the yarn passes from the friction twisting head 5. The yarn leaving the head 5 passes around a guide wheel 6 which is positioned so as to guide the yarn in optimum frictional contact with the operative part of the twisting head 5 as will be subsequently explained in greater detail. The yarn then passes to a driven yarn feeding arrangement 7 and then on to a package winder 8.

As the yarn approaching the friction head 5 is heated while in a twisted condition and undergoes cooling before the twist is removed, the yarn becomes set in a crimped configuration.

Referring now to FIG. 2, the friction head 5 (shown in full lines) is mounted on a support bracket 10 by means of a frame 12.

The frame 12 supports a journal ball bearing 13 in which a drive pulley 14, having a central boss 15, is mounted for rotation about a substantially vertical axis. The boss 15 has an axial through bore in which a flexible false twisting tube 17 is secured at its lower end by the compression of a screw collar 16 and is thus rotated by the pulley 14, the latter being driven by a belt 23.

The tube 17 is journalled in a roller bearing 20 at its upper end and in a further roller bearing 21 approximately midway between the bearing 20 and the boss 15, so constraining the tube into a generally curved path. As can be seen clearly in FIG. 2, the lower end portion of the tube as it passes through the boss 15 is straight and as the flexible portion leaves the boss it is curved sharply between the boss and bearing 21 after which the radius of curvature increases towards the bearing 20.

The tube in this embodiment therefore is curved in the form of part of a parabola, the portion of minimum radius of curvature being in the region of the boss 15 which in this case is the entry point of the yarn, and the portion of maximum radius of curvature being in the region of the bearing 20 which is the exit point of the yarn.

At each end of the tube 17 .is polished annular ceramic guide 19 which is mounted so as to be both rotatable and co-axial with the tube and each guide forms, in effect, a wear resistant extension of the tube.

The flared guides are dimensioned and arranged so that the bore of the tube 17, which is substantially constant throughout its length increases progressively in the extensions provided by the guides 19 so that yarn drawn through the tube can enter and leave the tube in frictional contact with a polished surface having a radius in the direction of travel of the yarn.

The tube is made of or has the surface of its bore lined or coated with a flexible material having high abrasion resistance combined with high frictional properties and is so constructed that its bore remains open during rotation to provide a continuous passageway for running yarn to be false twisted.

The tube 17 in the embodiment of FIG. 1 comprises a continuous inner surface lining of polyethylene or synthetic rubber in the form of a tube having an internal bore diameter of approximately 0.25 inches.

Externally of the lining tube is a helical spring 18 of fine gauge wire of circular cross section. The internal diameter of the spring helix is slightly smaller than the exterior diameter of the friction tube which lines it,

thus the frictional surface is given the necessary form and support, and the two parts act as one.

The tube is curved so as to have a minimum radius of curvature of about 1% inches as it leaves the boss 15,

increasing to about 3 inches as it enters the bearing 20.

The chain-dotted lower part of FIG. 1 illustrates an alternative construction in which the tube directs the yarn through substantially a right angle whereby the efficiency of the head'is increased due to the greater fric tional contact of the tube with the yarn passing through it.

FIG. 3 illustrates a different construction of false twisting friction tube 30 which can be used in place of the tube 17. The tube 30 is in fact a helix, which, when its longitudinal axis is straight has its successive turns closely adjacent to or touching each other so that it does in effect define a tube. The tube 30 consists of a helical spring formed of a plurality of turns of spring steel wire of rectangular cross section 31. The wire is wound in a precision helical form to leave a space between adjacent turns and a coating of friction material is bonded to the inner surface of the wire and extends overthe surfaces of the wires between successive turns of the helix 32, 33. The distance between adjacent turns of the helix and the thickness of the friction material is such that the surfaces of the friction material which extend between successive turns of the helix are brought together and the surfaces of the material facing inwards come together to form a continuous friction surface 36 along that side of the tube which has the smallest radius of curvature along its length.

The operation of the invention is carried out in the following manner with reference to FIG. 1 in which a yarn is shown threaded on a machine in such a way as to produce a false twist crimp. The, yarn Y is tensioned between the input device 2 and the feed device 7 and as it passes through the head 5 it is drawn against the internal surface of the friction tube 17 which is rotating. The guide wheel 6 is positioned to maintain the yarn in close contact with the friction tube up to the point of exit, then to guide it without drag to the yarn drive mechanism 7 which feeds it to the take up package.

Owing to the small internal radius of the friction tube, the line of contact between the yarn and the inter nal surface of the friction tube is maintained parallelto the axis of the tube throughout and lies in the plane of curvature of the tube. The axis of rotation of the yarn is also parallel to the axis of rotation of the friction tube at all points of contact between them.

The internal radius of the friction tube being constant throughout, each part of the yarn in contact with it is driven at the same rotational speed and the relative slip between the surface of the tube and the yarn is equal at all points of contact.

The gradual increase in the radius of axial curvature of the friction tube from the point of entry of the yarn onwards provides a means of maintaining a constant contact pressure between the yarn and the friction surface throughout the length of contact between them.

It will be appreciated that an important aspect of the method described is that the maximum possible twisting component is applied to the yarn by the friction surface with no differential effect due to variation in friction surface speed resulting from changes in the radius of rotation.

Another aspect of the method described is that owing to the axial alignment between the yarn and the friction surface, there are no driving or retarding components applied axially to the yarn. Owing to the frictional drag between the yarn and the internal surface of the tube over the long are of contact, the tension gradient within the head itself is sufficient to provide the necessary conditions for friction twisting with a relatively low input tension of around 0.1 grams per (lenier or less.

The radius of curvature of the tube can be variable in order to make it possible to adjust the tension gradient within the tube.

Various alternative constructions are possible depending upon the nature of the crimping process which is being carried out. For example, a pair of heads identical to those shown in the top half of FIG. 5 could be placed side by side with the tubes of the two heads extending generally parallel to one another but with the guide wheel 6 arranged to feed the yarn rising from one tube downwardly through the second tube which is rotating in the same sense to place a reverse twist in the yarn between the exit of the first tube and the surface of the second tube so as to produce a non-torque yarn.

Alternatively, two heads of the type shown in the top part of FIG. 5 may be arranged so that their upper ends are, as it were, face to face. If these tubes rotate in the same sense the yarn produced is similar to that produced by the construction of FIG. 2 but including the lower head shown in chain-dotted lines. But if the two heads rotate in opposite senses a non-torque yarn may be produced.

The arrangement shown in FIG. 1 utilizes a single pass heater but if desired the yarn, after leaving the drive wheel 7 can pass back through the heater or through a separate heater to provide second stage stabilizing.

Den- Fila- Through- Material ier ments Temp. out input outlet (f.p.m.) tension tension Nylon 66 I40 26 235C 400 lZ'kg. 80g. Dacron 200 47 2l0C 375 14g. 90g. Nylon 66 20 7 225C 400 2g. 20g.

For the above results a tube 3 inches long was employed having an inside diameter of 0.2 inch and a substantially constant radius of curvature of 1% inches. It was lined with silicone rubber and the speed of rotation was 8,400 r.p.m.

What we claim as our invention and desire to secure by Letters Patent is:

l. Yarn twisting apparatus incorporating at least one hollow twisting element which constrains a travelling yarn passing through such element to take up a curved path in contact therewith and having a rotary yarn engagement surface all parts of which are arranged to rotate at substantially identical peripheral speeds over the length of the curved contact path.

2. Yarn twisting apparatus comprising a flexible tube constrained to have a curved longitudinal axis and mounted for rotation about its longitudinal axis.

3. Apparatus as claimed in claim 2 in which at least the surface of the bore of the tube consists of a flexible material.

4. Apparatus as claimed in claim 3 in which the tube is formed of flexible material and has means for supporting it to maintain its bore open.

5. Apparatus as claimed in claim 4 in which the supporting means comprises a helix of spring material.

6. Apparatus as claimed in claim 2 in which the flexible tube is formed by a helix.

7. Apparatus as claimed in claim 6 in which the helix comprises a helical spring coated at least on its surface which faces the bore of the tube with a flexible material.

8. Apparatus as claimed in claim 2 in which the flexible tube is mounted for rotation in a number of spaced bearings.

9. Apparatus for false twisting yarn including means for heating a travelling yarn, a flexible tube constrained to have a curved longitudinal axis, means for rotating the tube about its longitudinal axis and means for linearly advancing a yarn in heat exchange relationship with the heater and through the tube while it is rotating so as to contact the internal wall thereof.

10. A method of twisting a yarn comprising traveling the yarn lengthwise in a curved path while contacting it with a rotary yarn engagement surface all parts of which are moving at substantially identical linear speeds over the length of the curved contact path.

11. A method according to claim 10 in which said engagement surface is the bore of a tube formed of flexible material and having a curved longitudinal axis about which the tube is rotated.

12. A method according to claim 10 in which the yarn is first heated.

13. A method as claimed in claim 10 in which the line of contact of the yarn and the engagement surface is parallel to the axis of rotation of the latter. 

1. Yarn twisting apparatus incorporating at least one hollow twisting element which constrains a travelling yarn passing through such element to take up a curved path in contact theRewith and having a rotary yarn engagement surface all parts of which are arranged to rotate at substantially identical peripheral speeds over the length of the curved contact path.
 1. Yarn twisting apparatus incorporating at least one hollow twisting element which constrains a travelling yarn passing through such element to take up a curved path in contact theRewith and having a rotary yarn engagement surface all parts of which are arranged to rotate at substantially identical peripheral speeds over the length of the curved contact path.
 2. Yarn twisting apparatus comprising a flexible tube constrained to have a curved longitudinal axis and mounted for rotation about its longitudinal axis.
 3. Apparatus as claimed in claim 2 in which at least the surface of the bore of the tube consists of a flexible material.
 4. Apparatus as claimed in claim 3 in which the tube is formed of flexible material and has means for supporting it to maintain its bore open.
 5. Apparatus as claimed in claim 4 in which the supporting means comprises a helix of spring material.
 6. Apparatus as claimed in claim 2 in which the flexible tube is formed by a helix.
 7. Apparatus as claimed in claim 6 in which the helix comprises a helical spring coated at least on its surface which faces the bore of the tube with a flexible material.
 8. Apparatus as claimed in claim 2 in which the flexible tube is mounted for rotation in a number of spaced bearings.
 9. Apparatus for false twisting yarn including means for heating a travelling yarn, a flexible tube constrained to have a curved longitudinal axis, means for rotating the tube about its longitudinal axis and means for linearly advancing a yarn in heat exchange relationship with the heater and through the tube while it is rotating so as to contact the internal wall thereof.
 10. A method of twisting a yarn comprising traveling the yarn lengthwise in a curved path while contacting it with a rotary yarn engagement surface all parts of which are moving at substantially identical linear speeds over the length of the curved contact path.
 11. A method according to claim 10 in which said engagement surface is the bore of a tube formed of flexible material and having a curved longitudinal axis about which the tube is rotated.
 12. A method according to claim 10 in which the yarn is first heated. 